Haar
A haar is a cold sea fog that rolls in from the North Sea onto the east coast of Scotland and England, often on otherwise fine days in spring and early summer. It forms when warm, moist air passes over cold sea water and cools until the moisture condenses into fog, which the wind then pushes inland.
In practice
Edinburgh sits on the Firth of Forth, so the haar can swallow Leith, Portobello and the New Town while the west of the city, a few miles inland, stays bright. It can arrive within an hour and lift just as quickly, and the temperature drops noticeably when it does. The Castle and Arthur's Seat can vanish entirely. In north-east England the same thing is called a sea fret.
Why it matters to newcomers
A sunny morning in May is not a promise of a sunny afternoon at the beach. Take a layer to Portobello, check the view from the Castle before paying for it, and do not be surprised if flights at Edinburgh Airport are briefly affected. Locals say "the haar's in" in the way others say it is raining.
Related
- Dreich - the other Scottish word you will need for the weather
- Outwith - a Scots word you will meet in the same breath as forecasts and notices
Source: Met Office: fog.